The present invention relates to a rotation angle sensor sensing a rotation angle of a rotary member, and more specifically to a rotation angle sensor sensing a throttle valve opening and an accelerator pedal opening of a vehicular engine.
U.S. Pat. No. 5,798,639 (corresponding to Published Japanese Patent Application Kokai No. H07(1995)-260412) shows a rotation angle sensor including a magnetic circuit and an electric circuit. The magnetic circuit is composed of a magnet provided in a rotary shaft rotating in accordance with a throttle valve opening, and yokes surrounding the magnet nearly over the full circumference. The electric circuit includes a magnetoelectric transducing element, such as a Hall effect device, disposed between the yokes, and a signal processing circuit.
The Hall effect device senses magnetic flux density varying in accordance with the rotation angle, in the magnetic circuit, and the signal processing circuit determines the rotation angle by processing a signal from the Hall effect device.